You cannot make up your own contract for me

I spoke to a consultant from MTN Direct called Marvin to cancel the my MTN contract after MTN billed me for an upgrade that I never received. Marvin told me he could move me back to my old contract which I had before the upgrade that took place in October 2017 which cost me R139 per month. But when I look at my most recent invoice from MTN then I am on a contract that costs me R260 per month. Now that is NOT what was agreed to. Please have Marvin contact me to I can cancel my contract with MTN.